The present disclosure pertains to wireless networking. In wireless networking, a frequency hopping system utilizes a method of transmitting radio signals by rapidly switching a carrier among many frequency channels, using a pseudorandom sequence known to both transmitter and receiver. In asynchronous frequency hopping systems, a radio transmits the time and frequency synchronization information in preamble (PRE) and synchronization (SYNC) slots only at the beginning of a call or communication session. Disadvantageously, if some target radios or devices (so-called late entrants) miss this initial synchronization information, they are unable to join the call or communication session at a later time. Another problem is that, even if the synchronization information is resent (e.g., sent at fixed, known frequencies) periodically among the traffic, it is not possible to ensure that the overall frequency hopping pattern stays random, as per U.S. Federal Communications Commission (FCC) requirements for frequency hopping systems. Yet another problem is that, if the synchronization information is resent using a different random hopping pattern based on a secondary hop seed (instead of using fixed frequencies) and it is interleaved among the traffic slots, it is difficult to ensure that the overall frequency hopping pattern stays random, and each of the frequencies are used with an equal chance, as per FCC requirements. This last case is also not possible because a receiver would not know what frequencies to listen to in the beginning, i.e. the PRE and SYNC always have to be on fixed, known frequencies.
Accordingly, there is a need for a method and apparatus for late entry in asynchronous frequency hopping systems using random permutation sequences.
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The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.